Method and device for melting the ends of rods

ABSTRACT

The invention relates to a method for treating the ends of glass rods in which glass rods are inserted into receptacles in a carrier and with the carrier are carried past a burner and at least one rail in an advancing direction, the flame of the burner melting at least one end of the glass rods and the glass rods being lifted by the rail in the receptacles and rolling on the rail so that the glass rods are made to rotate during the melting process.

FIELD OF INVENTION

The invention relates generally to the post-processing of rod-shapedmeltable material, in particular the melting of the ends of glass rods.

BACKGROUND OF THE INVENTION

Rod-shaped glass material, either a solid material or in the form oftubes, is subdivided for many applications into sections and thesesections re-used. For example, glass tube sections are used tomanufacture reed switches. Likewise, glass tube sections are also usedas packaging for other electrical and electronic components. Sections ofsolid glass rods are also used as light guides.

The sections are generally disconnected from the rod by breaking.However, the fractured edges can cause problems. Inter alia, fracturesstarting from the fractured edges can reduce the stability, have anadverse effect on the visual properties in the case of light guides andlead to leaks in glass tubes. The sharp edges which arise during thebreaking process are in many case undesired. In order to avoid theseproblems, it is appropriate to melt the ends. However, in this processit is possible for problems to occur if the melting does not take placeuniformly. In this case, it is possible, inter alia, fordisadvantageous, intolerable deviations from the desired dimensions ofthe sections to occur.

SUMMARY OF THE INVENTION

The invention is based on the object of permitting particularly uniformmelting of the ends of glass tube sections.

Accordingly, the invention provides a method for treating the ends ofglass rods in which glass rods are inserted into receptacles of acarrier, and with the carrier are carried past a burner and at least onerail in an advancing direction, the flame of the burner melting at leastone end of the glass rods, in particular the front face at this end, andthe glass rods being lifted by the rails in the receptacles and rollingon the rail so that the glass rods are made to rotate during the meltingprocess.

A corresponding device for treating the ends of glass rods, inparticular for carrying out the method according to the invention,comprises a burner, a carrier with receptacles for the insertion ofglass rods, an advancing device for carrying the carrier past theburner, and at least one rail which runs along the carrier and whoseupper side runs in the region of the carrier above the lowest point ofthe receptacle so that as the glass rods which are inserted into thecarriers pass the flame of the burner they are lifted by the rail bymeans of the advancing device in the receptacles and roll on the uppersides of the rail. The glass rods are preferably inserted intocorrespondingly configured receptacles transversely with respect to theadvancing direction.

An advancing device can comprise, in particular, a suitable conveyorbelt on which the carrier is placed. Such a conveying mechanism alsoeasily permits various kinds of carriers for various rod dimensions tobe conveyed.

The burner and the rails are preferably arranged in a stationaryfashion, in this case the carrier being carried past the burner.However, it is also possible that the advancing device does not move thecarrier past but instead moves the burner and the rails past astationary carrier. In terms of the rotation of the glass rods broughtabout by the rolling on the rail, the important factor is essentiallythe relative movement between the carrier and rail, which can be broughtabout with the two abovementioned possibilities and generally by arelative movement of rails and carrier, or its receptacles.

The invention makes available a very simple arrangement with whichuniform post-processing of the ends of the glass rods is brought about.The rolling of the glass rods during the melting in the flame bringsabout uniform heating of the ends of the glass rods. The melting inparticular also provides a smooth, fire-polished surface.

Furthermore, both ends of the glass rods, in particular the material atthe end faces, are preferably melted. For this purpose, burners arearranged on both sides of the carrier.

One embodiment of the invention provides that the glass rods are liftedon one side by a rail arranged to the side of the carrier, and roll onthis rail. According to another embodiment of the invention, the carrieris moved through between two spaced-apart rails, both ends being liftedin this case.

As a result of the rolling on the upper side of the rail, the glass rodsrotate, at an angular speed of v/r provided no friction or slip slowsdown the rotation. Here, v designates the advancing speed and rdesignates the radius of the glass rods.

In a further preferred configuration of the invention, there isprovision that the receptacles in the carrier are configured as recessesor depressions in the carrier. They can be adapted in particular to theshape of the glass rods. Good thermal contact is thus provided betweenthe glass rods and the carrier.

In order to bring about as uniform a heating as possible of the end orends of the glass rods, it is furthermore particularly preferred if theburner has a plurality of burner nozzles which extend in the advancingdirection. With such a power burner the ends of the glass rods are movedsuccessively through not just one individual flame but through aplurality of flames while the rods roll.

With the method according to the invention it is possible, inter alia,to smooth fractured edges of the glass rods. It is likewise alsopossible in the case of small glass tubes that one end of these smallglass tubes is closed by melting. In this way, small glass tubes whichare closed at one end are obtained. Such glass tubes are suitable, forexample, for encapsulating transponders or for manufacturing ampullas.

The method is suitable in particular for treating relatively small glassrods having a diameter in the range from 0.5 mm to 30 mm, preferably inthe range from 1 mm to 20 mm. In order to be able to process the variousformats of glass rods, in each case it is possible to prepare carrierswhose receptacles are embodied for the respectively specified diameters.

In one development of the invention, a heating device for the carrier isalso provided. The carrier can particularly advantageously be preheatedwith such a heating device. In particular, this preheating of thecarrier can be carried out with glass rods inserted. As a result, theparts of the glass rods which rest on the carrier are also preheated.This is favorable, inter alia, in order to avoid sudden transitions inthe glass rods as a result of excessively high temperature changestresses. A particular advantage is obtained particularly when treatingglass tubes. Heating the glass tubes on the carrier prevents depositionof condensates within the tubes when they are carried past the burner.The preheating is preferably carried out in multiple stages. Inparticular, it is possible for this purpose to place the glass rods on acarrier which is preheated in a first preheating step and to furtherpreheat carriers with glass rods in at least one further step before themelting process.

The following parameters have proven particularly favorable in order, onthe one hand, to avoid temperature stresses and, on the other hand, toobtain small tolerances in the form of the ends of the glass rods:

The advancing speed with which the glass rods are carried past theburner is preferably in the range from 0.1 to 10 cm/s, preferably in therange from 0.5 to 5 cm/s, and particularly preferably in the range from0.8 to 4 cm/s.

Furthermore it is favorable if the ends of the glass rods are flametreated by the burner for a duration in the range from 3 to 15 seconds,preferably in the range from 5 to 10 seconds.

In order to facilitate the flame treatment of the ends of the glassrods, it is also favorable if the rolling ends of the glass rods projectbeyond the rail.

Furthermore it is particularly advantageous if the rail is arrangedbetween the carrier and burner openings. In this way, the rail cansimultaneously act as a shield which prevents the burner carrying outflame treatment on other parts of the glass rods apart from their ends.In addition to one or more rolling bars on which the glass rods are madeto rotate by rolling on their upper side, it is furthermore alsoadvantageous to provide a run-up bar which runs in the advancingdirection. With this run-up bar, the position of the glass rods whichare carried past is aligned or arranged transversely with respect to theadvancing direction. In order to facilitate the lifting of the glassrods at the start of the rail, the rail is furthermore preferablybeveled at least one end in the advancing direction. Both ends of therail are preferably beveled so that the glass rods do not drop backabruptly into the receptacles after rolling on the upper side but ratherare positioned completely in the receptacles again after rolling slowlyon the oblique surface.

In terms of the burner, it is also preferred that the combustible gas isnot mixed in the nozzles of the burner but rather outside the nozzles ina mixer. The latter is preferably arranged upstream of a gas quantityregulator so that the combustible gas together with the oxidation agentwhich it contains is preferably regulated by air added by the mixer.This measure has surprisingly proven very favorable in obtaining a moresimple way of regulating the burner. In particular, even very lowoverpressures can then be regulated precisely in order to bring aboutuniform burning and thus also uniform post-treatment of the glass rodends, in particular their end faces.

In a further advantageous configuration of the invention, a burner isprovided which has two different systems of gas feed ducts with nozzlesarranged in an alternating fashion with respect to one another. As aresult, it is possible, inter alia, for combustible gas to be fed via atleast two gas feed ducts which are connected to a plurality of nozzleswhich are arranged in alternating fashion, in particular in theadvancing direction. In addition, in contrast to what is describedabove, the various components of the combustible gas can be fed andregulated separately via the nozzles or outlet openings which arearranged in an alternating fashion, said components can first be mixedwith one another above the nozzles during the combustion process.Finally, with systems of gas feed ducts which vary in such a way it isalso possible to feed two different combustible gases to the nozzles ina respectively alternating fashion. The various possibilities thuspermit inter alia, sensitive regulation and adaptation of various typesof glass in a way which is matched to the dimensions of the glass rodsto be treated.

A compact design for the burner with very fine ducts for the gas supplycan also be obtained if the gas supply system of the burner hasdepressions in a burner body, which depressions are closed to the side,preferably by the rail, and thus form ducts for the gas supply. As aresult of the covering with the rail it is possible also to ensure thatthe outlet openings of the ducts form burner nozzles which are verysmall and open directly at the rail. This ensures that the flames of theburner likewise burn directly at the rail. This is advantageous sincethe rail then produces a sharp delimitation of the heating zone alongthe glass rods to be treated, with selective heating of only the ends ofthe glass rods which project beyond the rail.

The glass rods which can be manufactured according to the invention aredefined by at least one, preferably two, fire-polished end faces. Inthis context, the very uniform and precisely adjustable melting processwhich is achieved according to the invention provides very tighttolerances in the deviations from the diameter and length. As a result,glass rods with a length dimension tolerance of at maximum 0.20 mm canbe manufactured. In terms of the external diameter, and/or in the caseof glass tubes also the internal diameter, it is possible to comply withdeviations of at maximum 0.08 mm, preferably only 0.05 mm.

The method and the device or the glass rods manufactured therewith can,inter alia, be used advantageously to manufacture reed relays, sensors,transponders and light guides.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail below by means ofexemplary embodiments and with reference to the appended drawings inwhich identical reference symbols refer to identical or similar parts.

In said drawings:

FIG. 1 is a view of parts of a device according to the invention,

FIG. 2 is a view of the arrangement illustrated in FIG. 1 in theadvancing direction of the carrier,

FIG. 3 shows a variant with rails arranged on each side of the carrier,

FIG. 4 is a view of the burner,

FIG. 5 is an enlarged view of a detail of the region X in FIG. 4,

FIG. 6 is a view of a carrier,

FIG. 7 is a side view of an arrangement composed of rolling rail andcarrier,

FIG. 8 is a diagrammatic overall view of an exemplary embodiment of adevice according to the invention, and

FIGS. 9 to 11 show examples of glass rods manufactured according to theinvention.

DETAILED DESCRIPTION

FIG. 1 shows parts of a device according to the invention which isdesignated in its entirety by the reference symbol 1. The device 1 fortreating the ends 91, 92 of glass rods 9 comprises a burner 3, a carrier5 with receptacles for placing the glass rods 9 in, an advancing device(not illustrated in FIG. 1) for carrying the carrier 5 past the burner 3in an advancing direction 11, and a rail 7 which runs along the carrier5 and whose upper side runs above the lowest point of the receptacles inthe region of the burner 3 so that as glass rods 9 which have beeninserted into the receptacles are carried past the flames of the burner5 said glass rods 9 are lifted by the rail 7 by means of the advancingdevice in the receptacles, and roll on the upper side of the rail 7. Inthe process, the glass rods 9 are carried past the burner 3 at anadvancing speed in the range from 0.1 to 10 cm/s, preferably in therange from 0.5 to 5 cm/s, particularly preferably in the range from 0.8to 4 cm/s. The advancing speed is preferably set here in such a way thatthe ends of the glass rods are flame treated by the burner by the flamesof the burner 3 for a duration in the range from 3 to 15 seconds,preferably in the range from 5 to 10 seconds, and the material at theend faces is melted.

As is apparent from FIG. 1, the glass rods are inserted in such a waythat their cylinder axes lie transversely with respect to the advancingdirection so that they can roll in the advancing direction over theirouter cylinder surface.

The arrangement shown in FIG. 1 and the mechanism of the will beexplained below in more detail with reference to the view shown in FIG.2. FIG. 2 shows the arrangement in the advancing direction 11. Theburner 3 is configured as a power burner with a plurality of nozzles 37which are arranged one behind the other, and for this purpose itcomprises a base body 30 with gas feed ducts 31, 32 which run in theadvancing direction. A plurality of ducts 34, 35 which are arranged onebehind the other in the advancing direction and run vertically in thisexemplary embodiment is connected to the gas feed ducts 31, 32 viabranching ducts 36. In this context, the ducts are divided into twogroups, the first group of ducts 34 being connected to the gas feed duct31, and the second group of ducts 35 being connected to the gas feedduct 35. This configuration of the invention will be described in moredetail below with reference to FIGS. 4 and 5. The ducts 34, 35 lead intoopenings 37 which constitute the burner nozzles.

The ducts 35 are embodied as milled elements which are closed off by therail 7 which is attached to the base body 30 of the burner 3.

Semicylindrical receptacles 51 in which the glass rods 9 to be treatedare placed are inserted into the upper side of the carrier 5. In orderto fire-polish the rod ends, the carrier 5 is then carried past the railin such a way that the base point, or the lowest point 52 of thereceptacles 51, runs below the upper side 71. In the process, the rods,which rest with their lateral surface on the base point 52, are eachlifted at one end 91 by the rail 7, as shown in FIG. 2, and roll on theupper side 71 of the rail 7, while the ends are flame treated by theflames 39 produced at the nozzle openings 37, and said ends melt as therods 9 roll.

However, the glass rods are not completely lifted out of the receptacles51 so that the rods are still carried and moved onward in thereceptacles.

The ends 91 of the glass rods project beyond the rail 7 and into theflames 39. The rail 7 which is arranged between the carrier 5 and theburner openings 37 also advantageously shields other parts of the glassrods 9 from the flame treatment, apart from their ends 91 of said glassrods 9. This prevents the glass rods from becoming too soft and beingable to bend or even melt between the ends 91, 92.

The glass rods 9 on the carrier are also carried past a run-up bar 15which runs in the advancing direction and their position is orientedtransversely with respect to the advancing direction. The transversealignment with respect to the advancing direction ensures that the ends91 all project equally far beyond the rail 7 and into the flames 39 ofthe burner, within the scope of the length tolerance.

In the example shown in FIG. 2, the glass rods are also lifted on oneside by means of an individual rail.

FIG. 3 shows a variant with rails 7 and burners 3 which are arranged oneach side of the carrier. In this variant, the carrier 3 is accordinglymoved through between the two spaced-apart rails 7, and both ends 91, 92of the glass rods 9 are lifted so that both ends 91, 92 of the glassrods 9 roll over the upper side 71 of the rails 7 and their outermostregions are melted.

FIG. 4 shows, for the purpose of further clarification of the structure,a view of the burner 3 such as is used in the exemplary embodiments inFIGS. 1 to 3. FIG. 5 is an enlarged illustration of the detail indicatedby X.

From FIGS. 4 and 5 it is apparent that the nozzles 37 which are arrangedin the advancing direction 11 are also assigned in an alternatingfashion to two different gas supply systems, one system being suppliedwith gas via the gas supply duct 31, and the other system via the gassupply duct 32. The ducts 34 which are connected to the gas supply duct31 and the ducts 35 which are connected to the further gas supply duct32 are embodied in each case here as depressions in the burner body 30,which depressions are then closed laterally by the rail 7 (notillustrated here) so that the combustible gas can escape only throughthe nozzles 37. By means of the nozzles 37 which are connected in analternating fashion to the gas supply ducts 31, 32 it is possible tooperate the burner, for example, as an externally mixing burner in thatcombustible gas and oxidizing agent are fed separately via the ducts 31,32 and escape through respectively adjacent nozzles 37. It is likewisepossible to feed premixed combustible gas, in which case it isadditionally possible to make available different combustible gases viathe ducts 31, 32 and/or to regulate the gas quantities through the ducts31, 32 separately.

FIG. 6 illustrates a view of an exemplary embodiment of a carrier 5. Thecarrier 5 comprises a base body which is elongated in the advancingdirection 11 and in whose upper side 53 a plurality of receptacles inthe form of recesses or depressions which are arranged one behind theother in the advancing direction. These recesses are semicylindricalwith a transverse cylinder axis with respect to the longitudinal extentof the carrier body or with respect to the advancing direction.Correspondingly, the cylindrical glass rods 9 can then be placed inthese depressions transversely with respect to the advancing direction11, as shown in FIG. 1.

The underside 54 of the carrier 5 is planar in this exemplary embodimentso that the carrier can easily be placed with this side on a conveyorbelt as an advancing device for carrying the carrier past the burner.

FIG. 7 shows in a side view an exemplary embodiment of a rail 7 such ascan be used in the arrangement shown in FIGS. 1 to 3, and a carrier 3and the mechanism of lifting and rolling the glass rods on the carrier 5by means of the rail 7.

As is illustrated once more in FIG. 7, the upper side 71 of the rail 7which runs along the carrier 5 in the advancing direction 11 lies abovethe lowest point 52 of the receptacles 51 in such a way that as glassrods 9 which are inserted into the receptacles are carried past theflame of the burner they are slightly lifted in the receptacles by therail by means of an advancing device and roll on the upper side 71 ofthe rail 7. For the purpose of clarity, only two glass rods 9 which havebeen inserted into the receptacles 51 are illustrated in FIG. 7.

In order to facilitate the lifting process, the upper side of the railis beveled at the end 73 to such an extend that the upper side 71 of therail 7 at this end runs under the lowest point of the receptacle, inparticular however under the lowest point of the lateral faces of theglass rods 9 which have been inserted into the receptacles 51. As thecarrier 5 is carried past the oblique surface, the ends of the glassrods 9 are then lifted uniformly on as far as the height of the planarregion of the upper side 71 of the rail 7 and can roll there. The otherend 75 of the rail 7 is also beveled so that after the melting processhas ended the glass rods 9 can again roll down the oblique surfaceuniformly and thus be placed gently in the receptacles 51.

FIG. 8 is a schematic view of an exemplary embodiment of a device 1according to the invention in its entirety. The device comprises a unit100 in which long glass rods 9 are divided into relatively short glassrods 9 by breaking and these relatively short glass rods 9 are placed onthe carrier 5. The carrier is preferably already preheated here.Preheating can be carried out electrically and/or by means of hot air. Aplurality of carriers 5 are used and they are conveyed one behind theother on a conveyor belt 110 as an advancing device. The carriers 5which are equipped in the unit 100 are then fed through two preheatingstages 102 and 104 in which the carrier, together with the glass rods 9placed in them are heated. An electrical heating or means of heating bymeans of warm air are appropriate for the first stage 102. The heatingin the second stage 104 is preferably carried out with one or moreburners.

The carriers which are heated by means of this multiple stage preheatingdevice with stages 102, 104 and glass rods 9 which are conveyed thereonare then fed by means of the conveyor belt 110 to a further unit 106 inwhich the flame polishing of the rod end is carried out by means of theinventive burner 3 with the rail (not illustrated), as explained withreference to the figures above. Finally, the carriers with theflame-polished glass rods are cooled in a defined fashion in a coolingunit 108.

After the conclusion of the processing steps shown in FIG. 8, thecarriers 5 can remain equipped and can be removed from the conveyor beltso that they serve simultaneously as magazines for the treated glassrods in order to carry out further manufacturing steps.

FIGS. 9 to 11 each show examples of glass rods 9 manufactured accordingto the invention, in a cross sectional view. The examples here each showglass rods in the form of glass tubes 80. Furthermore in all theexamples shown, both ends 91, 92 are treated and fire-polished bymelting the material at the end faces.

In the example shown in FIG. 9, in each case a small bead 82 has beenproduced at the end faces 93, 94 by the melting of the glass. This beadcan be advantageously used, inter alia, for attaching the small tube. Inthe exemplary embodiment illustrated in FIG. 10, the ends are onlyslightly melted so that fire-polished end faces 93, 94 with roundededges are obtained.

In the example illustrated in FIG. 11, in contrast to the examples inFIGS. 9 and 10 the end 92 of the small glass tube 80 has been closed bythe melting process so that a one-sided closure 95 is obtained. Suchsmall glass tubes can be used, for example, as ampullas orencapsulations for electrical or electronic components. Inter aliaencapsulation for transponders or sensors is meant here. The other end91 of this exemplary embodiment has been reshaped into an inwardlycurved collar 96 by the melting with the device according to theinvention. This collar 96 can advantageously be used to secureelectrical or electronic components or else to attach a closure for thisend 91.

In all the examples of small glass tubes shown, it is possible toachieve very tight tolerances in their dimensions. For example, themaximum external and/or internal diameters at the ends of the tubesshown can be fabricated with a maximum deviation of at most 0.08 mm,generally even only 0.05 mm. The small glass tubes 80 can also bemanufactured with deviations in terms of the length dimension of at most0.20 mm. This high precision results from the very uniform meltingprocess obtained according to the invention so that identical conditionsin terms of the temperature distribution and the treatment time areobtained for all the glass rods, and deviations in shape as a result ofthe melting are reduced to a minimum.

It is apparent to a person skilled in the art that the invention is notrestricted to the exemplary embodiment described above but rather can bevaried in a variety of ways. In particular, the features of theindividual exemplary embodiments can also be combined with one another.

1. A method for treating the ends of glass rods, the method comprising:inserting the glass rods into receptacles in a carrier; carrying theglass rods with the carrier past i) a burner and ii) at least one rail,in an advancing direction; and melting at least one end of the glassrods via the flame of the burner; wherein the glass rods in thereceptacles are lifted via the at least one rail and roll on the atleast one rail so that the glass rods are made to rotate during themelting process.
 2. The method as claimed in claim 1, wherein the glassrods are lifted on one side by a rail which is arranged to the side ofthe carrier, and roll on this rail.
 3. The method as claimed in claim 1,wherein the carrier is moved through between two spaced-apart rails andboth ends of the glass rods are lifted.
 4. The method as claimed inclaim 1, wherein both ends of the glass rods are melted.
 5. The methodas claimed in claim 1, wherein the glass rods are inserted intocorrespondingly configured receptacles, transversely to the advancingdirection.
 6. The method as claimed in claim 1, wherein the glass rodsrotate with an angular speed of v/r, v designating the advancing speedand r designating the radius of the glass rods.
 7. The method as claimedin claim 1, wherein the glass rods are placed in the receptacles in thecarrier which are configured as recesses or depressions in the carrier.8. The method as claimed in claim 1, wherein the ends of the glass rodsare moved successively through a plurality of flames while the rodsroll.
 9. The method as claimed in claim 1, wherein by melting the end ofthe glass rod a fractured end of the glass rod at this end is smoothed.10. The method as claimed in claim 1, wherein one end of small glasstubes is closed by the melting process.
 11. The method as claimed inclaim 1, wherein glass rods with a diameter in the range from 0.5 mm to30 mm are treated.
 12. The method as claimed in claim 1, wherein thecarrier, is preheated.
 13. The method as claimed in claim 12, whereinthe glass rods are placed on the preheated carrier and the carrier withthe glass rods is preheated in at least one further stage before themelting process.
 14. The method as claimed in claim 1, wherein the glassrods are carried past the burner at an advancing speed in the range from0.1 to 10 cm/s.
 15. The method as claimed in claim 1, wherein the endsof the glass rods are flame treated by the burner for a duration in therange from 3 to 15 seconds.
 16. The method as claimed in claim 1,wherein the rolling ends of the glass rods project beyond the rail. 17.The method as claimed in claim 1, wherein the rail shields other partsof the glass rods apart from their ends from the flame heating by theburner.
 18. The method as claimed in claim 1, wherein the glass rods onthe carrier are carried past a run-up bar which runs in the advancingdirection and their position is aligned transversely with respect to theadvancing direction.
 19. The method as claimed in claim 1, wherein theburner comprises combustible gas which is fed via at least two gas feedducts to nozzles arranged in an alternating fashion.
 20. The method asclaimed in claim 1, wherein the combustible gas is mixed in a mixeroutside the nozzles before a regulating means.
 21. A method formanufacturing, the method comprising: inserting glass rods intoreceptacles in a carrier; carrying the glass rods with the carrier pasti) a burner and ii) at least one rail, in an advancing direction;melting at least one end of the glass rods via the flame of the burner,wherein the glass rods in the receptacles are lifted via the at leastone rail and roll on the at least one rail so that the glass rods aremade to rotate during the melting process; and utilizing the meltedglass rods as part of one or more of reed relays, sensors, transponders,and light guides.